[gtk+] Use g_set_object in one more place

[Matthias Clasen <matthiasc src gnome org>]

commit 449fd4a350da32175961934617a4ecbdc2e04e16
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue May 3 22:15:17 2016 -0400

    Use g_set_object in one more place

 gtk/gtkcsswidgetnode.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtkcsswidgetnode.c b/gtk/gtkcsswidgetnode.c
index 294734e..3cce56d 100644
--- a/gtk/gtkcsswidgetnode.c
+++ b/gtk/gtkcsswidgetnode.c
@@ -137,8 +137,7 @@ gtk_css_widget_node_validate (GtkCssNode *node)
         gtk_style_context_validate (context, &change);
       else
         _gtk_widget_style_context_invalidated (widget_node->widget);
-      g_object_unref (widget_node->last_updated_style);
-      widget_node->last_updated_style = g_object_ref (style);
+      g_set_object (&widget_node->last_updated_style, style);
     }
   gtk_css_style_change_finish (&change);
 }